The present invention relates to a coin type electric element such as a coin type battery and a printed circuit board with a coin type electric element, which is mounted by soldering thereon.
A coin type electric element, such as a coin type battery and a coin type capacitor, has a pair of terminals in both ends. In such a coin type electric element, a sealing plate seals opening of the coin exterior case with a bottom, which encloses bottom side of the case. The sealing plate is fixed on the coin exterior case and held by an insulating seal interposed between them, and seals a coin exterior case alrtightly. The sealing plate is insulated from the coin exterior case by the insulating seal. The sealing plate and exterior case, which are insulated from each other, are used as a pair of electrodes. As shown in FIG. 1, in the coin type electric element of such a construction, the electrodes 105, which are the exterior case 103 and the sealing plate 10, are connected to a pair of leads 106 by spot welding. The ends of the two leads 106 are fixed on the conductive regions 109 of a printed circuit board 102 by soldering.
As shown in FIG. 1, the coin type electric element 101 mounted on the printed circuit board 102 by the two leads 106 by soldering. As shown in FIG. 2, soldering portions 106B of the coin type electric element 101 makes the mount area on the printed circuit board 102 large. The reason is that the soldering portions 106B of the leads 106 project outwardly from the coin type electric element 101. Further, such a construction has a disadvantage that the mount area becomes larger when the soldering portions of the leads are enlarged in order to be fixed firmly.
Furthermore, in such a construction, when the leads are shortened in order to make the mount area small, the coin type electric element mounted on the printed circuit board tends to have a thermal influence caused by a heated soldering iron or melted solder. Especially, It is important to heat the lead to high temperature capable of sufficient melting solder in order to fix the lead firmly on the printed circuit board. The reason is that insufficient heating the lead causes a cold joint. Insufficient heating the lead deteriorates the flow of the melted solder, therefore the solder can not be in intimate contact with a large area of the surface of the lead. Accordingly, it is Important to heat the lead sufficiently to avoid a cold joint. The lead is heated by the soldering Iron thrust thereon. When solder becomes the temperature capable of sufficient melting of It by heating, the solder on a soldering Iron flows along the surface of the lead, and spreads in a large area. In order to diffuse solder widely, it is necessary to heat the lead sufficiently by a soldering iron. An operator thrusts soldering Irons to the lead and heats it until the solder flows widely on the surfaces of the leads. In the case that a coin type electric element sensitive to heat is soldered, leads should be heated carefully. If the temperature of the leads is too high, the coin type electric element has a thermal influence. While, If the temperature of the leads is too low, it causes a cold Joint. Especially, in a method of using a soldering iron, an operator adjusts heating by soldering irons with a visual check of a state of the solder. Therefore, it is very difficult to keep ideal soldering consistently.
Reflow soldering can perform temperature control exactly as compared with the method of using a soldering iron, However, since reflow soldering heats altogether by a hot air current, not only the lead but also the coin type electric element are heated. Therefore, as shown in FIG. 1, when the ends of the both leads are fixed on to the printed circuit board by reflow soldering, heating the whole of the coin type electric element to high temperature can damage the coin type electric element.
The present invention is devised to solve the above problems, and is aimed at providing a coin type electric element, which can be mounted on a small mount area and can be fixed firmly and with stability on a printed circuit board by soldering, and can prevent from a thermal influence, and a printed circuit board with a coin type electric element, which is mounted by soldering thereon.
A coin type electric element of the present invention have a coin exterior case formed of metal and in a coin shape with a bottom and an opening; a sealing plate, which is fixed on the opening of the coin exterior case, sealing airtightly the coin exterior case; and an insulating seal, which is interposed between the coin exterior case and the sealing plate, insulating the coin exterior case from the sealing plate. In the coin type electric element, one of the bottom of the coin exterior case and the sealing plate as a pair of terminals is a first terminal face. The other of the bottom of the coin exterior case and the sealing plate as the pair of the terminals is a second terminal face. A first soldering face to be fixed by reflow soldering is provided on the first terminal face. A second soldering face to be fixed by reflow soldering is provided on a tip portion of a lead connected to the second terminal face. The first soldering face and the second soldering face are positioned substantially in a same plane.
In this specification, xe2x80x9cthe first soldering face and the second soldering face are positioned substantially in a same planexe2x80x9d is defined such that the first soldering face and the second soldering face are positioned at positions capable of reflow soldering together.
The coin type electric element is a coin type battery or a capacitor. Further, in the coin type electric element, the tip portion of the lead is bent toward a surface side of the first terminal face, and an insulating film 8 is provided on a position, which opposes to the bent portion, in a surface of the bottom of the coin exterior case or a surface of the sealing plate. Furthermore, the first soldering face in the first terminal face is plated with a metal having an affinity for solder. In addition, the first soldering face is provided by fixing a metal film on the first terminal face.
A printed circuit board with a coin type electric element of the invention have the coin type electric element having a coin exterior case formed of metal and in a coin shape with a bottom and an opening, a sealing plate, which is fixed on the opening of the coin exterior case, sealing the coin exterior case airtightly, and an insulating seal, which is interposed between the coin exterior case and the sealing plate, insulating the coin exterior case from the sealing plate, and a printed circuit board with conductive regions provided thereon, on which the coin type electric element is mounted. In the printed circuit board, a first terminal face, which is one of the bottom of the coin exterior case and the sealing plate as a pair of terminals, is fixed on one of the conductive regions without a lead interposed between the first terminal and the one of the conductive regions by reflow soldering. A second terminal face, which is the other of the bottom of the coin exterior case and the sealing plate as the pair of the terminals, is fixed on the other conductive region by a lead soldered by reflow soldering.
In the printed circuit board with a coin type electric element, the sealing plate as the first terminal face is fixed directly on the one of the conductive regions by the soldering, and the bottom of the coin exterior case second terminal face is fixed on the other conductive region by a lead soldered by the soldering. In addition, the bottom of the coin exterior case as the first terminal face is fixed directly on the one of the conductive regions by the soldering, the sealing plate as the second terminal face is fixed on the other conductive region by a lead soldered by the soldering.
The lead is bent toward a position between the coin type electric element and the printed circuit board, and the bent portion is fixed on the other conductive region by the soldering. This construction has an advantage that the area mounting the coin type electric element on the printed circuit board can be smaller. Further, an insulating film is provided on a position, which opposes to the bent portion. The insulating film can properly prevent electrical shorting between the bent portion of the lead and the first terminal face.
In the coin type electric element, the first terminal face, which is soldered on the conductive region of the printed circuit board, is plated with a metal having an affinity for solder. In addition, a metal film is fixed on the first terminal face, which is soldered on the one of the conductive regions, of the coin type electric element.
The temperature of a component, which is carried into a reflow soldering equipment, is proportional to the amount of heat absorbed, and is inversely proportional to its specific heat. The amount of heat absorbed increases according to an area. The specific heat is a constant specified with a material of a component. Therefore, a temperature of a component, whose surface area is large and whose specific heat is small, rises quickly. However, this is in the case without a change of state of a component. In the case that a state of a component changes from a solid state to a liquid state, the heat of fusion limits its temperature rise. The heat of fusion is large as compared with the specific heat, and limits a temperature rise remarkably. For example, in tin contained in solder, Its specific heat is 0.053 cal/g, while Its heat of fusion is 14 cal/g. In addition, in lead contained in solder, its specific heat and Its heat of fusion are 0.0309 cal/g, 5.5 cal/g respectively. The heat of fusion keeps the temperature of the solder heated at the melting point until the whole of solder is melted. After the whole of solder is melted, the temperature rises in proportion to the amount of heat absorbed. FIG. 10 is a graph showing the temperature rise of the solder against the amount of heat absorbed. As shown in FIG. 10, after solder, which changes from a solid to a liquid, is heated to melting point, the heat of fusion keeps the temperature of the solder heated at the melting point. After the whole of solder is melted into a liquid, its temperature rises gradually. Accordingly, solder temporarily limits its temperature rise around Its melting point. Solder, which limits its temperature rise, is in intimate contact with the first terminal face, and delays the temperature rise of the first terminal face. The first terminal face is a coin exterior case or a sealing plate. Thus, solder, which limits its temperature rise, delays the temperature rise of the exterior case or the sealing plate of the coin type electric element, and effectively prevents thermal influence. Especially, solder is in intimate contact with the first terminal face in a large area to fix the coin type electric element firmly on the printed circuit board. This improves the effect that solder limits the temperature rise of the first terminal face. Limiting the temperature rise of the first terminal face in a large area can prevent thermal influence in the coin type electric element. The exterior case or the sealing plate as the first terminal face is made of a metal with high thermal conductivity. Accordingly, limiting the temperature rise of the first terminal face in a large area limits the temperature rise of the coin type electric element, so that the maximum heated temperature of the insulating seal, etc. can be low. A coin type electric element is heated to the temperature close to its limit in order to prevent a cold Joint. Therefore, decreasing its temperature rise can extremely Improve reliability of a product, even the decreased temperature rise is not very much. The reason is that limiting under the maximum heated temperature can almost eliminate defectives caused of exceeding the maximum temperature of an insulating seal.
Furthermore, reflow soldering effectively limits the temperature rise of the first terminal face of the coin type electric element in a large area, but provides an environment in that solder is attached firmly by melting. Accordingly, reflow soldering effectively eliminates a cold Joint. The reason is that the temperature rises of the first terminal face, on which solder is attached by melting, the conductive regions, lead etc. are not limited by heat of fusion. That Is, although the temperature rises of solder and the first terminal face in contact with It are limited by heat of fusion, the temperature rise of a portion to be attached with melted solder is not limited. Therefore, reflow soldering provides an environment in that the temperature of the portion rises quickly. This provides ideal intimate contact of solder.
As mentioned above, as comparison between the state that the first terminal face of the coin type electric element fixed on the conductive region by reflow soldering and the state that a lead is soldered on a printed circuit board by soldering Iron, both of the heated solder are very different from each other. Solder on the tip of a soldering iron is already melted. Since melted solder and a soldering iron heat a lead and a conductive region, the temperature rises of a lead and a conductive region are not limited. In addition, a technology, in which leads of a coin type electric element connected to conductive regions of the printed circuit board without a soldering Iron by reflow soldering, has developed. In this technology, two leads connected to terminals of a coin type electric element are soldered by reflow soldering. That is, in the coin type electric element connected to the printed circuit board in this construction, both the first terminal face and the second terminal face are connected to leads, as shown in FIG. 1. The coin type electric element connected to the printed circuit board in this construction has a disadvantage that the coin type electric element receives thermal influence by heating during reflow soldering.
Further, a coin type electric element of the present invention have a coin exterior case formed of metal and in a coin shape with a bottom and an opening, a sealing plate, which is fixed on the opening of the coin exterior case, sealing the coin exterior case, and an insulating seal, which is interposed between the coin exterior case and the sealing plate, insulating the coin exterior case from the sealing plate. In the coin type electric element, one of the bottom of the coin exterior case and the sealing plate as a pair of terminals is a first terminal face. The other of the bottom of the coin exterior case and the sealing plate as the pair of the terminals is a second terminal face. A soldering face to be fixed by reflow soldering is provided on a tip portion of a lead, which is bent toward a surface side of the first terminal face and is connected to the second terminal face. The coin type electric element is a coin type battery or a capacitor. Furthermore, an insulating film is provided on a position, which opposes to the bent portion, in a surface of the bottom of the coin exterior case or a surface of the sealing plate.
A coin type battery and a printed circuit board with a coin type electric element of the present invention has an advantage that the coin type electric element can be mounted on a small mount area and can be fixed firmly and with stability on a printed circuit board by soldering, and can prevent from a thermal Influence. The reason is that the first soldering face to be fixed by reflow soldering is provided on the first terminal face, and a second soldering face to be fixed by reflow soldering is provided on the tip portion of the lead connected to the second terminal face, in the coin type electric element. Further, in the printed circuit board with a coin type electric element, the first terminal face, which is one of the bottom of the coin exterior case and the sealing plate as a pair of terminals, is fixed on one of the conductive regions by reflow soldering without a lead Interposed between the first terminal and the one of the conductive regions, and the second terminal face, which is the other of the bottom of the coin exterior case and the sealing plate as the pair of the terminals, is fixed on the other conductive region by a lead soldered by reflow soldering.
The construction, in which the first terminal face is directly fixed by reflow soldering, can reduce a mount area of the coin type electric element compared with a conventional construction, in which both terminals are fixed by leads. The reason is that the coin type electric element is fixed on the conductive regions by reflow soldering without outwardly projecting a soldering portion of a lead from the coin type electric element. As compared with a mount area defined as 100 of a printed circuit board with a conventional construction shown in FIG. 1 and FIG. 2, the mount area of printed circuit boards according to embodiments of the present invention shown in FIG. 3, FIG. 5 and FIG. 6 was 79, and the mount area of printed circuit boards according to embodiments of the present invention shown in FIG. 4, FIG. 7 and FIG. 8 was 70. These constructions can reduce mount areas remarkably.
Further, the construction, in which the first terminal face is fixed by reflow soldering without a lead, has an advantage that the coin type electric element is effectively prevented from a thermal influence caused by heating the whole of coin type electric element to high temperature. The reason is that the temperature rise of soldering is limited and the temperature rise of the first terminal face is delayed by the heat of fusion of solder melted from a solid to a liquid. The temperature rise of melted solder is temporarily limited around melting point by the heat of fusion. Thus, the temperature rise of the exterior case as the first terminal face or the sealing plate is limited by melted solder, so that the whole of coin type electric element can be effectively prevented from being heated to high temperature. Especially, it can more effectively prevent the temperature rise that solder is in intimate contact with the first terminal face in a large area and the coin type electric element is firmly fixed on the printed circuit board.
Furthermore, the coin type electric element of the present invention, in which the first soldering face and the second soldering face are positioned substantially in a same plane, has an advantage that fixing the first soldering face and the second soldering face together by reflow soldering bring a high effective mass production.
A printed circuit board with a coin type electric element of the present invention has the coin type electric element having a coin exterior case formed of metal and in a coin shape with a bottom and an opening, a sealing plate, which is fixed on the opening of the coin exterior case, sealing the coin exterior case, an insulating seal, which is interposed between the coin exterior case and the sealing plate, insulating the coin exterior case from the sealing plate, a printed circuit board with conductive regions provided thereon, on which the coin type electric element is mounted, and a lead connected to the second terminal face. In the printed circuit board, one of the bottom of the coin exterior case and the sealing plate as a pair of terminals is a first terminal face, the other of the bottom of the coin exterior case and the sealing plate as the pair of the terminals is a second terminal face. The second terminal face is fixed on a conductive region of the printed circuit by a lead with a soldering face to be soldered by reflow soldering at an tip portion of the lead, which is bent toward a surface side of the first terminal face.